The objective of the proposed research is to apply knowledge gained from basic research to the understanding of human ocular motor disorders. Our effort will emphasize 1) quantitative measurements of ocular motor function in both human beings and monkeys and 2) control systems analysis to interpret our data. Our first major interest is in the role of the cerebellum in eye movement control. We will investigate in depth carefully selected groups of patients with abnormalities of ocular fixation related to cerebellar dysfunction as well as trained monkeys with experimental lesions in the cerebellum. We will measure the function of the vestibular, pursuit, optokinetic, and saccadic systems and with the aid of computer simulations compare the effects of simulated $ lesions to the ocular motor behavior of our patients and experimental animals. Our investigations should 1) provide new information about the neural control and anatomic substrate for both normal and pathologic eye movements, 2) enhance topical neuro-ophthalmologic diagnosis through more precise clinico-pathological correlations and 3) ultimately enable us to use the techniques to the treatment of the disabling visual disturbances that frequently plague patients with ocular motor disorders and cerebellar disease.